Issn 1021-4437, Russian Journal of Plant Physiology, 2007, Vol. 54, No. 6, pp. 790-796. Pleiades Publishing, Ltd., 2007
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ISSN 1021-4437, Russian Journal of Plant Physiology, 2007, Vol. 54, No. 6, pp. 790–796. © Pleiades Publishing, Ltd., 2007. Original Russian Text © V.N. Zholkevich, M.S. Popova, N.V. Zhukovskaya, 2007, published in Fiziologiya Rastenii, 2007, Vol. 54, No. 6, pp. 885–891.
790 INTRODUCTION Recently, we have described the stimulatory effects of neurotransmitters on root water-pumping activity [1]. Similar neurotransmitter action was also noted in earlier publications [2–8]. It manifests in the enhanced exudation of detached roots and is related to the increased root pressure due to its metabolic component, the increased temperature coefficient of exudation (Q
10
), a reduced exudate osmotic pressure, and decreased root hydraulic conductivity. It turned out that a stimulatory effects of all neurotransmitters tested (acetylcholine, adrenalin, noradrenalin, and serotonin) was completely abolished in the presence of microfila- ment- and microtubule-disrupting drugs and also uncouplers of oxidative phosphorylation. The effects of aforementioned agents were not limited by only neu- tralizing of neurotransmitter stimulatory action. Exuda- tion was suppressed to the same degree as in the pres- ence of only cytoskeleton drugs or oxidative phospho- rylation uncouplers in the absence of neurotransmitters [4, 5, 7]. This fact is especially important. It could indi- cate that, during exudation stimulation, the targets of neurotransmitters are energy-dependent contractile systems. This supposition is confirmed by the absence of any additivity of various neurotransmitter stimulat- ing effects at their combined application in each com- binations [5]. The reason for such additivity absence could be a commonness of neurotransmitter targets, and the cytoskeleton is evidently such a target. Stimulatory Effects of Adrenalin and Noradrenalin on Root Water-Pumping Activity and the Involvement of G-Proteins V. N. Zholkevich, M. S. Popova, and N. V. Zhukovskaya Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya ul. 35, Moscow, 127276 Russia; fax: 7 (495) 977-8018; e-mail: Zhvn@ippras.ru
Received April 12, 2007 Abstract
—To evaluate the involvement of G-proteins in the signal transduction during stimulatory action of neurotransmitters, adrenalin and noradrenalin, on root exudation and the ivolvement of G-proteins in water transport in the root and creaction of the root pressure, we tested the effects of guanosinethiodiphosphate, an inhibitor of GTP-binding capacity of G-proteins, and guanosinethiotriphosphate, a stimulator of this capacity. Experiments were performed with detached roots of 5–7-day-old maize ( Zea mays
L.) seedlings and the mittens produced from them due to the removal of the vascular cylinder. The latter are a convenient model to study the nature of the root pressure due to its strongly limited possibility to function as an osmometer during the early step of exudation. In the “mittens,” adrenalin and noradrenalin enhanced exudation, increased its temperature coefficient (Q
10
), root pressure, and its metabolic component much stronger than in detached roots with the vas- cular cylinder retained (conventionally named as “intact” roots). In control treatment (with water), guanosineth- iodiphosphate retarded exudation on the average by 30% in intact roots and by 50% in mittens, simultaneously reducing Q
10
from 3.0 to 1.7 in intact roots and from 4.0 to 1.3 in mittens. Guanosinethiotriphosphate exerted an opposite action: it stimulated exudation on the average by 30% in intact roots and by 60% in mittens; the Q
10
value increased from 3.0 to 3.6 in intact roots and from 4.0 to 5.8 in mittens. These data indicate that G-proteins are involved in the control of water transport and creation of the root pressure (without any other treatments). Guanosinethiodiphosphate neutralized completely adrenalin- and noradrenalin-induced stimulation of exuda- tion, resulting in the level substantially below the control one, especially in mittens. Guanosinethiotriphosphate enhanced stimulatory effects of both neurotransmitters, mainly in mittens, whereas its effect on intact roots was relatively weak, especially in experiments with noradrenalin. It should be emphasized that the mittens responded to both neurotransmitters and the regulators of G-protein activity much stronger than intact roots. The data obtained argue for the G-protein involvement in (1) transduction of adrenalin and noradrenalin signals stimulating root water-pumping activity and (2) the control of water transport and creation of the root pressure under normal conditions. Experiments with mittens indicate that this G-protein involvement could by mainly related to the functioning of the root cortex parenchymal cells and the formation of the metabolic component of the root pressure. DOI:
10.1134/S1021443707060118 Key words: Zea mays - root - mittens - exudation - signal transduction - G-proteins - neurotransmitters - gua- nosinethiodiphosphate - guanosinethiotriphosphate RESEARCH PAPERS Abbreviations
: MC—metabolic component; OP—osmotic pres- sure; RP—root pressure. RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
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STIMULATORY EFFECTS OF ADRENALIN AND NORADRENALIN ON ROOT 791
pathways of neurotransmitter signals related to exudate stimulation. The data presented in [1] permitted a sup- position about the involvement of protein kinases and protein phosphatases in the control of water transport and creation of the root pressure in control and under neurotransmitter action. Therefore, it seems likely that G-proteins, messengers in signal transduction from the plasma membrane receptors to downstream compo- nents of the signaling pathways, protein kinases and protein phosphatase in particular [9], could also be involved in these processes. The objective of this work was to elucidate the involvement of G-proteins in transduction of signals induced by adrenalin and noradrenalin and stimulating root water-pumping activity and the involvement of these proteins in the control of water transport and cre- ation of the root pressure. MATERIALS AND METHODS Experiments were performed with detached roots of etiolated maize seedlings ( Zea mays
L., hybrid Pioner). Plants were grown at
23°ë for 5–7 days. Thereafter, seedlings with straight primary roots 12–15 cm in length were selected. The root apical parts 5 cm in length were cut with a safety razor and used in further work.
Along with these root fragments, we used so-called “mittens” prepared from them. To this end, roots were bent at a distance of 7
− 8 cm from the apex in such a way that the cortex was broken and then removed care- fully the vascular cylinder, trying not to damage the root apical part. During vascular cylinder removal, the endodermis was ruptured. Thus, the mittens comprised the rhizodermis, cortex, and some cells of the broken endodermis; an elongated empty space was instead of the vascular cylinder (figure). Thus, it did not contained xylem and a xylem sap. When the removed vascular cylinder was shorter than the mitten by more than 0.5 cm, such mittens were discarded. Thereafter, the mitten was cut in the water drop with a safety razor, so that its length was 5 cm, i.e., was equal to the length of the root with the vascular cylinder, also used in experiments. This root part will be called further as intact root as dis- tinct from the mitten. Thus, we compared the behavior of intact roots and the mittens. When the mitten was fastened in water ver- tically in such a way that its upper part was above the water surface, the liquid penetrated its inner hollow, and in some time the mitten starts to exudates like the intact root with the vascular cylinder retained. The exu- dation rate of the mittens exceeded markedly that of intact roots. Exudation in the mitten started in spite of the absence of any solution, like the xylem sap, in its hollow. According to the classical osmotic theory of exudation, just the xylem sap sucks water from external medium [3, 7]. However, the mitten exudes under con- ditions strongly limiting a possibility of the mitten functioning as an osmometer. Thus, exudation started only due to only metabolic component, and later, when the inner hollow is filled with the exudates, the osmotic component of the root pressure begins to function as well. Thus, the mittens are a convenient model system to study the nature of the driving force of exudation [3, 7]. The advantage of the mittens is that the hypothesis of 1 2 3 4 4 5 6 5 2 1
(b) (c) (a)
The scheme of mitten obtaining from a detached maize root. (a) Root apical part; (b) removed vascular cylinder; (c) the mitten. ( 1
) Rhizodermis ( 2
) cortex; ( 3
) endodermis; ( 4
) vas- cular cylinder; ( 5
) remained cells of broken endodermis; ( 6
) elongated narrow hollow produced after the vascular cylin- der removal. 792
RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
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ZHOLKEVICH et al.
“asymmetric double membrane”, which neglect the occurrence of the metabolic component of the root pressure, and also the hypothesis about apoplastic channels of the vascular cylinder, which, in opinion of some researchers, are represent the principal mecha- nism of the root pressure [10–14], could not be applied to the mittens. The rate of exudation (
described in [15] in the U-10 thermostat (Germany) at
30°ë for 1 h, recording values every 20 min. Both intact roots and the mittens were preliminarily kept in the ultrathermostat for 10 min to equilibrate temperature. In the case of the mittens, we limited exposure to 20 min because we were interested in the observations during the initial stages of exudation when the contri- bution of the osmotic component to the root pressure was the lowest. A temperature coefficient of exudation (Q
10
) was calculated as the ratio of the J w
at 30°ë
to that
at
20°ë . Exudate osmotic pressure (OP
i
) was estimated by a microcryoscopic method, using the Osmonat osmometer (Gonotec, Germany). The driving force of exudation (root pressure) was determined by the compensatory method, as described in [1]. Hydraulic conductivity was measured using the pressure chamber [16], applying to the root external pressure, which was chosen experimentally and was equal to 20 kPa. To reveal the involvement of G-proteins in the con- trol of water transport and transduction of correspond- ing signals, we applied the inhibitor of their GTP-bind- ing activity, guanosinethiodiphosphate, and its activa- tor, guanosinethiotriphosphate. We used such concentrations of neurotransmitters and guanosinethiotriphosphate, which stimulated exu- dation of control intact roots by approximately 30%, and such concentration of guanosinethiodiphosphate, which suppressed exudation of control intact roots slightly stronger than by 30%. Finally, we used
10
–6
M adrenalin,
10 –5
M noradrenalin,
2 ×
10
–5 M guano- sinethiotriphosphate, and
2 ×
10
–5 M guanosinethio- diphosphate. We used noradrenalin hydrotartrate, the tetralithium salt of guanosinethiotriphosphate, and the trilithium salt of guanosinethiodiphosphate from Sigma (United States), and adrenalin hydrochlide obtained from Mos- cow Endocrine Plant. Settled tap water served a con- trol; it was also used for the preparation of all solutions. Experiments were performed in 10–20 replications with 8 samples each (see table notes for conditions for each experiment). Statistical data processing was per- formed using the program Microsoft Exel. The mean values and their standard errors are presented. RESULTS AND DISCUSSION Table 1 present the basic parameters of exudation from intact roots and the mittens. It is easy to note that exudation from the mittens was much intense and its temperature coefficient Q
10 was higher than in intact roots; the values of the root pressure (RP) and its meta- bolic component (MC) were also higher in the mittens. This agrees completely with our previous data [3, 7, 17, 18] and also with the data about enhanced pulsation activity of the cortical cells as compared with the cells of the vascular cylinder [19]. Treatments with neurotransmitters tested, adrenalin and noradrenalin, affected exudation from the mitten clearly stronger than for intact roots: they increased the exudation rate, its temperature coefficient Q
10
, enhanced the root pressure and its metabolic compo- nent stronger in the mittens (Tables 2, 3). The effects of guanosinethiotriphosphate (a stimula- tor of G-protein GTP-binding activity) and guano- sinethiodiphosphate (an inhibitor of G-protein GTP- binding activity) on the exudation rate in both control treatments and in the presence of neurotransmitters was opposite. These effects were stronger pronounced in experiments with the mittens than in experiments with intact roots. It is important to emphasize that, in control treat- ment, guanosinethiotriphosphate stimulated and gu- anosinethiodiphosphate suppressed exudation in the mittens much stronger than in intact roots. In the latter, guanosinethiotriphosphate stimulated exudation on the average by 30%, whereas in the mittens by 60%; gua- nosinethiodiphosphate retarded exudation approxi- Table 1.
Characteristics of exudation of intact roots and mittens (exposure of 20 min) Treatment J w
, µ
l/cm
2
for 20 min Q
10 OP
i
, kPa RP, kPa MC kPa RP Intact roots 52 Mittens
64
Notes: J w
—the rate of exudation; Q 10
—temperature coefficient of the rate of exudation in the range from 20 to 30
° C; RP—root (compen- satory) pressure; MC—metabolic component of the RP. Percents of the control values (100%) are indicated below horizontal lines. Twenty experiments with eight replicates each were performed. 1.3 0.1
± 100
--------------------- 3.0
0.2 ± 100 --------------------- 200
20 ± 100 --------------------- 420
10 ± 100 --------------------- 220
20 ± 100 --------------------- 3.1
0.3 ± 238 --------------------- 4.0
0.3 ± 133 --------------------- 250
30 ± 125 --------------------- 700
30 ± 167 --------------------- 450
30 ± 204 --------------------- RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
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STIMULATORY EFFECTS OF ADRENALIN AND NORADRENALIN ON ROOT 793
the mittens (Table 4). Both abovementioned regulators of G-protein activity changed Q
10
of exudation mar- kedly: guanosinethiotriphosphate increased and guano- sinethiodiphosphate reduced this coefficient. These changes were stronger pronounced in the mittens as
Characteristics of exudation of intact roots treated with adrenalin and noradrenalin (exposure of 20 min) Treatment J w
, µ
l/cm
2 for 20 min Q
OP
i
, kPa RP, kPa MC
L
p , %
kPa RP Control 52 100
Adrenalin, 1
× 10
–6
M 64 87 Noradrenalin, 1
× 10
–5
M 62 80
Notes: J w
—the rate of exudation; Q 10
—temperature coefficient of the rate of exudation in the range from 20 to 30
° C; RP—root (compen- satory) pressure;
—hydraulic conductivity; MC—metabolic component of the RP. Percents of the control values (100%) are indi- cated below horizontal lines. Twenty experiments with eight replicates each were performed. 1.3
0.1 ± 100 --------------------- 3.0
0.2 ± 100 --------------------- 200
20 ± 100 --------------------- 420
10 ± 100 --------------------- 220
20 ± 100 --------------------- 1.7
0.1 ± 131 --------------------- 3.3
0.2 ± 110 --------------------- 160
10 ± 80 --------------------- 450
10 ± 107 --------------------- 290
10 ± 132 --------------------- 1.7
0.2 ± 131 --------------------- 3.4
0.2 ± 113 --------------------- 180
20 ± 90 --------------------- 470
10 ± 112 --------------------- 290
20 ± 132 --------------------- Table. 3. Characteristics of exudation of the mittens treated with adrenalin and noradrenalin (exposure of 20 min) Treatment J w , µ l/cm 2
for 20 min Q 10 OP i , kPa RP, kPa MC
, % kPa
RP Control
64 100
Adrenalin, 1 × 10 –6 M 78 80 Noradrenalin, 1 × 10
–5
M 73 62 Notes: Designations as in Table 2. Twenty experiments with eight replicates each were performed. 3.1 0.3
± 100
--------------------- 4.0
0.3 ± 100 --------------------- 250
30 ± 100 --------------------- 700
30 ± 100 --------------------- 450
30 ± 100 --------------------- 4.4
0.3 ± 142 --------------------- 5.0
0.3 ± 125 --------------------- 210
30 ± 80 --------------------- 820
10 ± 117 --------------------- 640
30 ± 142 --------------------- 4.8
0.3 ± 155 --------------------- 5.2
0.2 ± 130 --------------------- 220
30 ± 88 --------------------- 800
30 ± 116 --------------------- 590
30 ± 131 --------------------- Table 4. Effects of guanosinethiodi- and triphosphate on the exudation rate (J w ) and its temperature coefficient (Q 10 ) in intact roots and mittens of the control treatment (exposure of 20 min) Root material Treatment
, µ l/cm 2 for 20 min Q 10 Intact roots water guanosinethiotriphosphate, 2 × 10
–5 M guanosinethiodiphosphate, 2 × 10
–5 M Mittens water guanosinethiotriphosphate, 2 × 10
–5 M guanosinethiodiphosphate, 2 × 10
–5 M Notes: Percents of control are indicated under horizontal lines. Ten experiments with eight replicates each were performed. 1.3 0.1
± 100
--------------------- 3.0
0.3 ± 100 --------------------- 1.7
0.1 ± 131 --------------------- 3.6
0.2 ± 120 --------------------- 0.9
0.2 ± 69 --------------------- 1.7
0.2 ± 57 --------------------- 3.1
0.3 ± 100 --------------------- 4.0
0.3 ± 100 --------------------- 4.9
0.3 ± 158 --------------------- 5.8
0.3 ± 145 --------------------- 1.4
0.1 ± 45 --------------------- 1.3
0.2 ± 33 --------------------- 794 RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
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ZHOLKEVICH et al. well: guanosinethiotriphosphate increased Q 10 in the
intact roots from 3.0 to 3.6, whereas in the mittens, from 4.0 to 5.8; guanosinethiodiphosphate reduced Q 10 in the intact roots from 3.0 to 1.7, whereas in the mit- tens, from 4.0 to 1.3. These results indicate unambiguosly the possible involvement of G-proteins in the control of water trans- port and creation of the root pressure in control intact roots and mittens (without any treatments). Since the reagents affecting G-proteins exerted a stronger action on exudation Q 10 in the mittens, which indicates espe- cially substantial role of complex metabolic processes in their water-pumpimg activity, than in intact roots, we could suppose the relationship between metabolic com- ponent of the root pressure (playing a principal role in exudation of the mitten) and G-protein functioning. As evident from Tables 5 and 6, guanosinethio- diphosphate not only neutralized the stimulatory effect of adrenalin and noradrenalin on exudation but also retarded exudation to the level below control one; its action was stronger in the mittens than in intact roots. However, guanosinethiodiphosphate-induced retarda- tion of exudation in the presence of adrenalin and nora- drenalin was much weaker that in the presence of only guanosinethiodiphosphate (Tables 5, 6). Thus, the pres- ence of neurotransmitters was beneficial for exudation even during G-protein inhbition. We observed similar pattern during protein kinase inhibition by staurospo- rine: retardation of exudation in the presence of adren- alin and noradrenalin was weaker than under the influ- ence of stausporine only on the exudation from control roots [1]. It seems likely that a signal induced by neu- rotransmitters and related to stimulation of root water- pumping activity could be transduced also without the involvement of G-proteins and protein kinases, i.e., through some other pathways. As was aforementioned, oppositely to guanosine- thiodiphosphate, guanosinethiodiphosphate enhanced exudation of both intact roots and the mittens in control treatment (Table 4). At the same time, its treatment in combination with adrenalin enhanced exudation of both root types (especially strongly in the case of mit-
) in intact roots and mittens (exposure of 20 min) Root material Treatment
µ l/cm 2 for 20 min % Intact roots water 1.3
± 0.1
100 adrenalin, 1 × 10
–6 M 1.7 ± 0.1
131 guanosinethiodiphosphate, 2 × 10
–5 M 0.9 ± 0.2
69 adrenalin, 1 × 10
–6 M + guanosinethio- diphosphate, 2 × 10 –5 M 1.2 ± 0.2
92 Mittens
water 3.1
± 0.3
100 adrenalin, 1 × 10
–6 M 4.4 ± 0.3
142 guanosinethiodiphosphate, 2 × 10
–5 M 1.4 ± 0.1
45 adrenalin, 1 × 10
–6 M + guanosinethio- diphosphate, 2 × 10 –5 M 2.6 ± 0.2
83 Notes: Procents of control are indicated under horizontal lines. Ten experiments with eight replicates each were performed. Table 6. Effects of noradrenalin and guanosinethiodiphosphate on the exudation rate (J w ) in intact roots and mittens (expo- sure of 20 min) Root material Treatment
µ l/cm 2 for 20 min % Intact roots water 1.3
± 0.1
100 noradrenalin, 1 × 10
–5 M 1.7 ± 0.1
131 guanosinethiodiphosphate, 2 × 10
–5 M 0.9 ± 0.2
69 noradrenalin, 1 × 10
–5 M + guanosinethio- diphosphate, 2 × 10 –5 M 1.1 ± 0.1
85 Mittens
water 3.1
± 0.3
100 noradrenalin, 1 × 10
–5 M 4.8 ± 0.3
155 guanosinethiodiphosphate, 2 × 10
–5 M 1.4 ± 0.1
45 noradrenalin, 1 × 10
–5 M + guanosinethio- diphosphate, 2 × 10 –5 M 1.7 ± 0.2
55 Notes: Percents of control are indicated under horizontal lines. Ten experiments with eight replicates each were performed. RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
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2007 STIMULATORY EFFECTS OF ADRENALIN AND NORADRENALIN ON ROOT 795 tens (Table 7)), whereas its combination with noradren- alin affected only the mittens (Table 8). Thus, some differences still were found in the path- ways of adrenalin and noradrenalin signal transduction related to the stimulation of root water-pumping activ- ity involving G-proteins, although these neurotransmit- ters are believed to be agonists. The differences noted were small. In general, the results of experiments with detached maize seedling roots and the mittens prepared from these roots argue for the involvement of G-proteins in (1) transduction of neurotransmitter (adrenalin and noradrenalin) signals related to the stimulation of root water-pumping activity and (2) the control of water transport and creation of the root pressure. These pro- cesses occur mainly in the root cortex parenchymal cells and are related to the formation of the metabolic component of the root pressure. ACKNOWLEDGMENTS This work was supported by the Russian Foundation for Basic Research, project no 06-04-48522. REFERENCES 1. Zholkevich, V.N., Zhukovskaya, N.V., and Popo- va, M.S.,The Involvement of Protein Kinases and Pro- tein Phosphatases in Signal Transduction during Neu- rotransmitter-Induced Stimulation of Root Water-Pump- ing Activity, Russ. J. Plant Physiol., 2007, vol. 54, pp. 487–490. 2. Zholkevich, V.N., Sinitsyna, Z.A., Peisakhzon, B.I., Abutalybov, V.F., and D’yachenko, I.V., Nature of the Root Pressure, Sov. Plant Physiol., 1979, vol. 26, pp. 978–993. 3. Zholkevich, V.N., Root Pressure, Plant Roots: The Hid- den Half, Waisel, J., Eshel, A., and Kafkafi, U., Eds., New York: Marcel Dekker, 1991, pp. 589–603. 4. Zholkevich, V.N. and Chugunova, T.V., Relationship between Cytoskeletal Proteins, Biomediators, and Phy- tohormones during Water Transport Regulation in Plants, Dokl. Akad. Nauk, 1995, vol. 341, pp. 122–125. 5. Zholkevich, V.N. and Chugunova, T.V., Effect of Neuro- mediators on Root Water-Pumping Activity, Dokl. Akad. Nauk, 1997, vol. 356, pp. 122–125. 6. Zholkevich, V.N., Zubkova, N.K., and Korolev, A.V., Effect of Colchicine and Noradrenalin on Helianthus
) in intact roots and mittens (exposure of 20 min) Root material Treatment
µ l/cm 2 for 20 min % Intact roots water 1.3
± 0.1
100 adrenalin, 1 × 10
–6 M 1.7 ± 0.1
131 guanosinethiodiphosphate, 2 × 10
–5 M 1.7 ± 0.1
131 adrenalin, 1 × 10
–6 M + guanosinethio- diphosphate, 2 × 10 –5 M 1.9 ± 0.1
146 Mittens
water 3.1
± 0.3
100 adrenalin, 1 × 10
–6 M 4.4 ± 0.3
142 guanosinethiodiphosphate, 2 × 10
–5 M 4.9 ± 0.1
158 adrenalin, 1 × 10
–6 M + guanosinethio- diphosphate, 2 × 10 –5 M 5.3 ± 0.3
171 Notes: Percents of control are indicated under horizontal lines. Ten experiments with eight replicates each were performed. Table 8. Effects of noradrenalin and guanosinethiotriphosphate on the exudation rate (J w ) in intact roots and mittens (expo- sure of 20 min) Root material Treatment
µ l/cm 2 for 20 min % Intact roots water 1.3
± 0.1
100 noradrenalin, 1 × 10
–5 M 1.7 ± 0.2
131 guanosinethiodiphosphate, 2 × 10
–5 M 1.7 ± 0.1
131 noradrenalin, 1 × 10
–5 M + guanosinethio- diphosphate, 2 × 10 –5 M 1.7 ± 0.1
131 Mittens
water 3.1
± 0.3
100 noradrenalin, 1 × 10
–5 M 4.8 ± 0.3
155 guanosinethiodiphosphate, 2 × 10
–5 M 4.9 ± 0.1
158 noradrenalin, 1 × 10
–5 M + guanosinethio- diphosphate, 2 × 10 –5 M 5.6 ± 0.2
180 Notes: Percents of control are indicated under horizontal lines. Ten experiments with eight replicates each were performed. 796 RUSSIAN JOURNAL OF PLANT PHYSIOLOGY
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15. Borisova, T.A., Lazareva, N.P., and Zholkevich, V.N., Possible Physiological Role of the Endodermal Jump of Water Potential in the Root System, Sov. Plant Physiol., 1984, vol. 31, pp. 1092–1098. 16. Savel’ev, V.A., Melekhov, E.I., and Abisalov, R.S., Mea- surement of Root Resistance to Water Flow with a Pres- sure Chamber, Vodnyi rezhim rastenii v svyazi s raznymi ekologicheskimi usloviyami (Plant Water Regime as Related to Various Ecological Conditions), Kazan: Kazan. Gos. Univ., 1978, pp. 384–388. 17. Zholkevich, V.N. and Chugunova, T.V., Participation of Parenchymal Cells in the Root Water-Pumping Activity,
18. Zholkevich, V.N., Gusev, N.A., Kaplya, A.V., Paho- mova, G.I., Pil’shchikova, N.V., Samuilov, F.D., Slav- nii, P.S., and Shmat’ko, I.G., Vodnyi obmen rastenii (Plant Water Relations), Tarchevsky, I.A. and Zholkevich, V.N., Eds., Moscow: Nauka, 1989. 19. Mozhaeva, L.V., Pil’shchikova, N.V., and Zaitseva, N.V., Investigation of Contractile Properties in Root Cells as Related to Plant Exudation Rhythms, Izv. Timiryazevsk. S-kh. Akad., 1975, no. 1, pp. 3–12. Yüklə 158,42 Kb. Dostları ilə paylaş:
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